# def fact(n):
#     if n == 1:
#         return 1
#     return n * fact(n - 1)
# print(fact(30))

# def fact(n):
#     return fact_iter(n, 1)

# def fact_iter(num, product):
#     if num == 1:
#         return product
#     return fact_iter(num - 1, num * product)

# def move(n, a, b, c):
#     if n == 1:
#         print(a, '-->', c)

# 期待输出:
# A --> C
# A --> B
# C --> B
# A --> C
# B --> A
# B --> C
# A --> C
# move(3, 'A', 'B', 'C')

# L = []
# n = 1
# while n <= 99:
#     L.append(n)
#     n = n + 2
# print(L)